Better NLP engine

[rtsao]

There's lots of false positives/negatives because the underlying NLP engine isn't that great.

Adopting https://stanfordnlp.github.io/CoreNLP/ might be an attractive alternative. By default, this plugin could possibly use the existing http://corenlp.run demo server, but allow for a different server via an environment variable.

Deploying your own CoreNLP server with docker is pretty straightforward.